That's what I thought they were trying to say... so I put, "I feel like a spider" ... so using "como" seems like it makes more sense if you're trying to say that.. I'm a native English speaker, but como is what they use for Spanish...but in that case, it might be "Estou como uma aranha." Because estar seems to be more relevant for a feeling...(at least with Spanish)...

A scene in Rio
Blu: [as they're walking in the jungle] Oh! Oh! What was that?
Jewel: A stick.
Blu: Ah! And that?
Jewel: It's just a rock.
Blu: Oh, right. Yeah.
[Blu stops and shudders as he feels something on his back]
Blu: Is that a spider on my back?
Jewel: Will you quit it? É apenas uma folha! It's just a leaf! Turn around!
[Blu turns and we see a huge spider on his back]
Jewel: Oh, um...
[Jewel quickly hits the spider off of Blu's back]
Jewel: Leaf. Told ya. http://www.imdb.com/title/tt1436562/quotes?item=qt1529768